Lars Von Trier is concerned about the state of Danish-Icelandic relations. "The fact is, we have a lot of Icelandic people who are buying most of Copenhagen right now," he says. "For 400 years, Iceland was under the Danish crown. All the Icelandic people hate the Danes in that sense. They have freaked themselves out about the Danes."

The subject is on his mind because of his amiable, witty new film, The Boss of It All, in which the middle-aged owner of a Danish IT firm tries to sell his company, with the prospective buyer being an Icelandic businessman - a situation that makes a few sly points about relations between the two countries. The film also highlights an oddly masochistic streak in the Danish sense of humour: they seem to adore being told how stupid they are. "They loved it in The Kingdom when people talked about the stupid Danes," Von Trier says, referring to his 1994 TV series. "Here, when the Icelandic people scream at them and say all these nasty things, they really love it."

Von Trier's office is located in a cottage at the edge of Filmbyen, the former military barracks outside Copenhagen where his production company Zentropa is based. In the complex where he edits his films, the walls are painted green, just as they reportedly are on Death Row in certain US prisons. There are Mao slogans in Danish scrawled on the plaster. These, I am told, reflect the fact that Von Trier's business partner, Peter Aalbeck Jensen, is "an old communist".

From the window, you can see a collection of garden gnomes - a gift from an American film company. They're called the "piss gnomes" because Aalbeck Jensen likes to urinate on them.

The pair of them operate as a good cop/bad cop couple, alternating roles. "It is very unDanish to be a bad cop," Von Trier observes. "Everyone in Denmark wants to be a good cop, but the bad cop is someone who is needed. As soon as you go to the UK or US, the bad cops are there because they are needed, but the Danish people are very, very afraid of conflict."

On the day I visit, there is a sign on the door of the main offices, where Zentropa employees have their lunch, announcing that there will be no hymn singing. Aalbeck Jensen, whose father was a priest, usually conducts Zentropa's Friday morning songs of praise, but is away on a bicycling holiday. Von Trier has decided at the last minute that he doesn't want to take his place. "I couldn't do it. It's not my scene. So I had to disappoint everybody."

Von Trier turned 50 earlier this year. Not long before his birthday, he issued a "Statement of Revitality" to mark his half-century. "In the last few years I have felt increasingly burdened by barren habits and expectations - my own and other people's - and I feel the urge to tidy up," he declared.

Tidying up in his case means no more trips to exotic film festivals, a reduction in his PR activities, a less structured routine, more time to develop his scripts, and a general "narrowing down".

It is a moot point whether Von Trier really is revitalised by his new system of working. The director is a keen gardener and claims he was delighted to miss Cannes this year because it gave him time to tend his vegetables. He also offers an idyllic image of his day-to-day life: "walking around the small woods with my iPod and dreaming", and playing the occasional game of tennis against Zentropa staff.

However, one guesses he is neither as relaxed nor as satisfied as he seems. The shoot of The Boss of It All was, he admits, as hectic and nerve-racking as ever. He only had five weeks in which to complete the movie - a satirical comedy set almost entirely in an office. It was shot on a lowish budget and in Danish, without the American and international stars who appeared in his last two films, Dogville and Manderlay. And it begins in a disconcerting fashion with a voiceover from Von Trier, where he tells his audience: "Here comes a film. It's a comedy and harmless."

Can a Lars Von Trier film ever be harmless? "Well," the director says, "I felt like saying that. I had been criticised for being too political and maybe I criticised myself for that. This is a film that was made very fast. This film is not political and I had fun doing it, but good comedies are not harmless."

Von Trier being Von Trier, The Boss of It All has one very perverse twist: it was made without a cameraman. The director was using a new process, "developed with the intention of limiting human influence", which he has called Automavision. This entails choosing the best possible fixed camera position and then allowing a computer to choose when to tilt, pan or zoom. "For a long time, my films have been handheld," he explains. "That has to do with the fact that I am a control freak. With Automavision, the technique was that I would frame the picture first and then push a button on the computer. I was not in control - the computer was in control."

Surely, I suggest, forfeiting so much of his own influence to a machine must have been an alarming step for a film-maker to take. "I found it a very fresh way of working," he says. "I am a man of very many anxieties but doing strange things with the camera is not one of them."

Besides, one of the main reasons for using Automavision was to ensure the actors couldn't use any of their usual tricks. Thanks to the randomised framing and audio settings, they had no idea of how the camera was going to behave and therefore weren't able to try to show off their best side or steal scenes. (Von Trier's original idea had been to hide the camera altogether and film through a double mirror, "but we had too little light. We couldn't do it".)

Von Trier says it was "liberating" and "relaxing" to be working in Danish, with a small crew. And he is embracing comedy. As well as The Boss of It All, he also recently wrote a comedy screenplay (which he won't direct himself), called Erik Nietzsche - The Early Years, based on his film-school days in the late 1970s, the period when he decided to add the "Von" to his original name, Lars Trier. "I was extremely irritating," he says about himself in those days. "I was very demanding. I wanted to know about the techniques of film but the teachers taught a lot of nonsense."

None the less, you can't help feeling the flirtation with comedy is simply a short respite before the director tackles some more daunting challenges. As he recently told his friend and former teacher Jorgen Leth, "the moment you cannot put yourself through hell any more, or you don't feel like it any more, that's probably the time to call it a day." There is no sign that he has reached that point yet.

You suspect, too, that Aalbeck Jensen will want Von Trier to stay in the limelight. His films help to keep Zentropa in business and if he is not making them or promoting them, the company's cash flow is bound to suffer.

In the long run, Von Trier is still determined to finish his American trilogy with Washington, even though critics have accused him of being virulently anti-American. When Dogville premiered in Cannes, Variety called it "an artistically experimental, ideologically apocalyptic blast at American values that is as obvious in intent as it is murky in aesthetic achievement." However, Von Trier, who still hasn't read the review, insists that he is a fan of American culture. "I must say I am as anti-Danish as I am anti-American, but it's OK. I don't mind being called anti-American. There's a big part of America I like - but then there is a part that I am not so crazy about."

Now he is "a little child of 50 looking for what comes up", Von Trier says he hopes he is becoming less serious. It would be a mistake, though, to think the enfant terrible of Danish cinema is lightening up. "Anxiety is taking yourself very seriously," he says - and it seems he is as anxious as ever.

· The Boss of It All premieres at the London film festival on October 19 and 20 at the Odeon West End, London WC2. Box office: 020-7928 3232